Screen printing is an old and established way of creating designs on various substrates, such as textile fabric, paper, metal, wood, glass, etc. Screen printing is essentially a stencil method of printing where the stencil is formed by a screen stretched over a wooden or metal frame. For finer detail, a finer mesh screen is used.
Early versions of screen printing used silk to form the screen. A design was created by painting the screen with a greasy medium. The pores of the silk were then closed using a suitable gum. The pores of the silk in the areas covered by the greasy medium were not closed because the greasy medium rejected the gum. Thereafter, the greasy medium was washed away with a solvent, such as turpentine, if paint was used as the greasy medium, resulting in the corresponding areas becoming pervious to ink. The screen was then placed on the surface of the substrate to be decorated and ink was applied through the screen to the surface using a rubber squeegee. The ink soaked through the pervious areas of the silk and was imprinted on the substrate.
More recent versions of screen printing use fine mesh screen materials rather than silk. The chosen screen material is coated with a photographic emulsion. The photographic emulsion is exposed to a suitable source of light with the image to be reproduced being located between the light and the emulsion. The light causes the emulsion to harden except in areas where the image is located. Thereafter, the screen is washed, which removes the emulsion from the areas where it has not been hardened by the light, i.e., the image areas. Then, the screen is used to print a design on a substrate.
In recent times, screen printing has been widely used to create a variety of single and multi-colored designs on a variety of textile fabric items, particularly clothing, such as T-shirts and sweatshirts. Various machines have been developed to improve screen printing. Unfortunately, the majority of such machines, particularly those designed to create multi-colored designs, are large and complex and, thus, expensive. Others are heavy, cumbersome, deteriorate rapidly, and lack adjustability.
In order to overcome the foregoing disadvantages, the All-in-one Screen Printing Machine described in U.S. Pat. No. 5,355,791 by John R. Benedetto and William Gillespie, Jr., was developed. The screen printing machine described in U.S. Pat. No. 5,355,791 is designed to be easily reconfigured to: (i) create an image-bearing screen; (ii) use the image-bearing screen to print designs on textile fabrics and other suitable substrates; and (iii) heat the design to set the print ink. The machine includes a metal cabinet with a horizontal shelf located beneath the top of the cabinet. Mounted on the metal shelf is a source of ultraviolet (UV) light. The upper ends of the metal cabinet walls are configured to receive a work surface suitable for supporting an image of the design to be printed and a framed screen. The image is preprinted on a sheet of material that passes UV light except where the image is located; and the screen is coated with a photographic emulsion. When exposed to the UV light, the photographic emulsion hardens, except where the image prevents the light from striking the emulsion. After exposure, the emulsion is washed to remove the remaining soft, unexposed (image) parts of the emulsion, creating a print screen. The all-in-one screen printing machine also includes an adjustable platen, preferably formed of metal, that is positioned just below the upper walls of the cabinet. The platen is suitable for supporting a piece of textile fabric, preferably in the form of a garment, such as a T-shirt, or other substrates suitable for receiving printing ink. The textile fabric or other substrate is mounted on the platen, which is positioned just below the print screen; and a squeegee is used to push the ink through the image apertures in the screen onto the fabric. A partially mechanical and partially manual registration mechanism allows print screens to be removed to inspect ink distribution and returned to their prior position if additional ink is required. The all-in-one screen printing machine also includes a heater positionable above a printed item to heat and cure the ink after it is applied.
While the all-in-one screen printing machine described in U.S. Pat. No. 5,355,791 is a substantial improvement over prior art screen printing machines, it is subject to improvement particularly in the areas of platen adjustability and the mechanism for supporting and registering a print screen. The present invention is directed to providing such an improved screen printing machine.